Anonymous
Jan 9
Describe the life cycle of schistosoma spp ?
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Jan 9
The life cycle of Schistosoma spp., also known as blood flukes, involves two hosts: a definitive host (human) and an intermediate host (snail). The life cycle can be divided into several stages:
1. Egg Production: Adult female Schistosoma worms reside in the blood vessels of the human host, where they produce eggs. These eggs are then released into the bloodstream and excreted in the urine or feces of the infected individual.
2. Miracidium: Once the eggs are released into freshwater, they hatch and release free-swimming larvae called miracidia. These miracidia must find and infect a specific species of freshwater snail, which serves as the intermediate host.
3. Sporocyst: Inside the snail, the miracidium transforms into a sporocyst, which undergoes asexual reproduction to produce numerous daughter sporocysts.
4. Cercaria: The daughter sporocysts further develop into cercariae, which are the infective stage for humans. Cercariae are released from the snail and swim freely in the water, actively seeking out human hosts.
5. Penetration: When a human comes into contact with contaminated water, the cercariae penetrate the skin, usually through hair follicles or sweat glands, and enter the bloodstream.
6. Migration: Once inside the human host, the cercariae migrate through various tissues and organs, eventually reaching the blood vessels of the liver or intestines, depending on the Schistosoma species.
7. Pairing and Mating: Male and female worms pair up and migrate together to the final location where they will reside, such as the mesenteric veins in the case of Schistosoma mansoni. Here, they mate and produce eggs, completing the life cycle.
The eggs produced by the adult worms can cause various health problems, as they can become lodged in the liver, intestines, or other organs, leading to inflammation, fibrosis, and other complications associated with schistosomiasis.
1. Egg Production: Adult female Schistosoma worms reside in the blood vessels of the human host, where they produce eggs. These eggs are then released into the bloodstream and excreted in the urine or feces of the infected individual.
2. Miracidium: Once the eggs are released into freshwater, they hatch and release free-swimming larvae called miracidia. These miracidia must find and infect a specific species of freshwater snail, which serves as the intermediate host.
3. Sporocyst: Inside the snail, the miracidium transforms into a sporocyst, which undergoes asexual reproduction to produce numerous daughter sporocysts.
4. Cercaria: The daughter sporocysts further develop into cercariae, which are the infective stage for humans. Cercariae are released from the snail and swim freely in the water, actively seeking out human hosts.
5. Penetration: When a human comes into contact with contaminated water, the cercariae penetrate the skin, usually through hair follicles or sweat glands, and enter the bloodstream.
6. Migration: Once inside the human host, the cercariae migrate through various tissues and organs, eventually reaching the blood vessels of the liver or intestines, depending on the Schistosoma species.
7. Pairing and Mating: Male and female worms pair up and migrate together to the final location where they will reside, such as the mesenteric veins in the case of Schistosoma mansoni. Here, they mate and produce eggs, completing the life cycle.
The eggs produced by the adult worms can cause various health problems, as they can become lodged in the liver, intestines, or other organs, leading to inflammation, fibrosis, and other complications associated with schistosomiasis.
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